The state of Washington enacted legislation requiring the state building code council to adopt a building code that incorporates the international codes and that is applicable throughout the state. See Rev. Code Wash. 19.27.031, 19.27.074. While the state has had its own radon control standard for new construction in place for a number of years, in 2007 the building code council formally incorporated the 2006 International Residential Code, along with Appendix F, into the state residential code. See Wash. Admin. Code 51-51-60101. The Washington code lists the seven Washington counties that are designated as Zone 1 counties (based on the EPA Map of Radon Zones) and must thus incorporate the radon control requirements of Appendix F into their local codes. The radon control requirements also apply in other counties to any structure constructed with an unvented crawlspace.